A Review on Electrospun Poly(amino acid) Nanofibers and Their Applications of Hemostasis and Wound Healing

The timely and effective control and repair of wound bleeding is a key research issue all over the world. From traditional compression hemostasis to a variety of new hemostatic methods, people have a more comprehensive understanding of the hemostatic mechanism and the structure and function of different types of wound dressings. Electrospun nanofibers stand out with nano size, high specific surface area, higher porosity, and a variety of complex structures. They are high-quality materials that can effectively promote wound hemostasis and wound healing because they can imitate the structural characteristics of the skin extracellular matrix (ECM) and support cell adhesion and angiogenesis. At the same time, combined with amino acid polymers with good biocompatibility not only has high compatibility with the human body but can also be combined with a variety of drugs to further improve the effect of wound hemostatic dressing. This paper summarizes the application of different amino acid electrospun wound dressings, analyzes the characteristics of different materials in preparation and application, and looks forward to the development of directions of poly(amino acid) electrospun dressings in hemostasis.

Elastic Nanofibrous Membranes for Medical and Personal Protection Applications: Manufacturing, Anti-COVID-19, and Anti-Colistin Resistant Bacteria Evaluation

Herein, in the present work two series of thermoplastic polyurethane (TPU) nanofibers were manufactured using the electrospinning techniques with ZnO and CuO nanoparticles for a potential use as an elastic functional layer in antimicrobial applications. Percentages of 0%, 2 wt%, and 4 wt% of the nanoparticles were used. The morphological characterization of the electrospun TPU and TPU/NPs composites nanofibers were observed by using scanning electron microscopy to show the average fiber diameter and it was in the range of 90-150 nm with a significant impact of the nanoparticle type. Mechanical characterization showed that TPU nanofiber membranes exhibit excellent mechanical properties with ultra-high elastic properties. Elongation at break reached up to 92.5%. The assessment of the developed nanofiber membranes for medical and personal protection applications was done against various colistin resistant bacterial strains and the results showed an increment activity by increasing the metal oxide concentration up to 83% reduction rate by using TPU/ZnO 4% nanofibers against K. pneumoniae strain 10. The bacterial growth was completely eradicated after 8 and 16 h incubation with TPU/ZnO and TPU/CuO nanofibers, respectively. The nanofibers SEM study reveals the adsorption of the bacterial cells on the metal oxides nanofibers surface which led to cell lysis and releasing of their content. Finally, in vitro study against Spike S-protein from SARS-CoV-2 was also evaluated to investigate the potent effectiveness of the proposed nanofibers in the virus deactivation. The results showed that the metal oxide concentration is an effective factor in the antiviral activity due to the observed pattern of increasing the antibacterial and antiviral activity by increasing the metal oxide concentration; however, TPU/ZnO nanofibers showed a potent antiviral activity in relation to TPU/CuO.

Selective antifungal and antibacterial activities of Ag-Cu and Cu-Ag core-shell nanostructures synthesized in-situ PVA

A simple chemical reduction method was employed to synthesize Cu-Ag and Ag-Cu core-shell nanostructures inside polyvinyl alcohol (PVA) matrix at room temperature. The core-shell nanostructures have been synthesized by varying the two different concentrations (i.e. 0.1 and 0.01 M) of the respective metal ions in equimolar ratios using successive reduction with hydrazine hydrate (HH) as a reducing agent. The core-shell nanostructures have been further characterized by different characterization techniques. The UV-visible spectroscopy exhibit the respective shift in the band positions suggesting the formation of core-shell nanostructures, which was further confirmed by field emission transmission electron microscopy-high-angle-annular dark field elemental mapping. The effect of metal ion concentration of the core-shell nanostructure on various Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and one fungal species Aspergillus fumigatus was observed by performing MIC and MBC/MFC study. Cu-Ag core-shell nanostructures were found to be effective antibacterial agent against all tested Gram-positive and Gram-negative bacteria, whereas Ag-Cu core-shell nanostructures were more efficient against a particular fungal species known as A. fumigatus. The highest value of MIC (75 µg ml^-1) for Ag-Cu 0.1M core shell nanostructures (D1) was noted against S. aureus and E. coli whereas the lowest value (20 µg ml^-1) was observed with P. aeruginosa. While in case of Cu-Ag 0.1M core shell nanostructures (E1) the highest value of MIC (100 µg ml^-1) was noted against S. aureus and P. aeruginosa whereas the lowest value (15 µg ml^-1) was observed with A. fumigatus. Also, field effect scanning electron microscope (FESEM) images of untreated and core-shell nanoparticles treated micro-organisms showed that 0.1 M Ag-Cu and 0.1 M Cu-Ag core-shell nanostructure can successfully break the cell wall of the fungi A. fumigatus and bacteria P. aeruginosa, respectively. Thus the present study concludes that, Cu-Ag & Ag-Cu core-shell nanostructures damage the cell structure of micro-organisms and inhibits their growth. Hence, the present Cu-Ag & Ag-Cu core-shell nanostructure acts as good antimicrobial agent against the bacteria and fungi, respectively.

Boronate sol-gel method for one-step fabrication of polyvinyl alcohol hydrogel coatings by simple cast- and dip-coating techniques

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities. A mixture of PVA and DBA in aqueous ethanol is prepared as a coating agent. The long pot life of the mixture allows for the coating of a wide range of materials with hydrogel films by simple cast- and dip-coating techniques. The resultant films show negligible dissolution in water and the intrinsic hydrophilicity of PVA provides the films with functional properties, such as improved antifogging property and resistance to protein and cell fouling. The self-assembling process shows adaptive inclusion properties toward nanoscale materials, such as metal–organic coordination polymers and inorganic nanoparticles, affording composite films. Furthermore, the coating film exhibits a unique secondary functionalization reactivity toward boronic acid-appended fluorescent dyes, through which a variety of materials are converted into fluorescent materials.

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities.

Thermosensitive Behavior and Super-Antibacterial Properties of Cotton Fabrics Modified with a Sercin-NIPAAm-AgNPs Interpenetrating Polymer Network Hydrogel

Poly(N-isopropylacrylamide) (PNIPAAm), sericin (SS), and silver nitrate were combined to prepare an interpenetrating network (IPN) hydrogel having dual functions of temperature sensitivity and antibacterial properties. The structure and size of AgNPs in such an IPN hydrogel were characterized by the Fourier Transform Infrared spectrum (FT-IR), X-ray powder diffraction (XRD) and Transmission Electron Microscope (TEM), and the thermal properties of the IPN hydrogel were characterized by Differential Scanning Calorimetry (DSC). Based on XRD patterns, Ag⁺ was successfully reduced to Ag⁰ by SS. It was observed by TEM that the particle size of silver particles was lower than 100 nm. The glass transition temperature (Tg) of IPN hydrogel was better than that of the PNIPAAm/AgNPs hydrogels, and lower critical solution temperature (LCST) values of the IPN hydrogel were obtained by DSC i.e. 31 °C. The thermal stability of the IPN hydrogel was successfully determined by the TGA. This IPN hydrogel was then used to modify the cotton fabrics by the "impregnation" method using glutaraldehyde (GA) as the cross-linking agent. The structures and properties of IPN hydrogel modified cotton fabric were characterized by scanning electron microscopy (SEM), FT-IR, and the thermogravimetry analysis (TGA). The results show that NIPAAm was successfully polymerized into PNIPAAm, and that there were neglected new groups in the hydrogel IPN. The IPN hydrogel was then successfully grafted onto cotton fabrics. SEM observations showed that the IPN hydrogel formed a membrane structure between the fibers, and improved the compactness of the fibers. At the temperature close to LCST (≈31 °C), the entire system was easily able to absorb water molecules. However, the hydrophilicity tended to decrease when the temperature was higher or lower than the LCST. The antibacterial rates of the modified cotton fabric against S. aureus and E. coli were as high as 99%.

Combined algicidal effect of urocanic acid, N-acetylhistamine and l-histidine to harmful alga Phaeocystis globosa

The algicidal compounds produced by Bacillus sp. strain B1 against Phaeocystis globosa, one of the main red-tide algae, were isolated and identified in a previous study as urocanic acid (uro), l-histidine (his) and N-acetylhistamine (ace). The 96 h median effective concentration EC50 values indicated the algicidal effect order of uro (8 μg mL-1) > ace (16 μg mL-1) > his (23 μg mL-1). The interaction between uro and ace had a synergistic effect on Phaeocystis globosa, accelerated the increase in its intracellular reactive oxygen species (ROS) levels, and further decreased the activities of antioxidases after 96 h, causing destruction of cell membrane integrity and nuclear structure. However, the other two binary mixtures uro + his and ace + his were both antagonistic to Phaeocystis globosa. The increase in the level of ROS indicated that the algal cells suffered from oxidative damage. The surplus ROS induced the increase in malondialdehyde (MDA) content and activities of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT), all of which reached maxima after 72 h treatment. Transmission electron microscopy (TEM) analysis revealed that these nitrogen-containing compounds caused destruction of cell membrane integrity, chloroplasts and nuclear structure. The present study will provide useful information for the combined effect of algicidal compounds on the harmful alga Phaeocystis globosa. This is the first report to explore single and combined algicidal effects of three nitrogen-containing compounds against the harmful alga Phaeocystis globosa.

Fabrication of ascorbyl palmitate loaded poly(caprolactone)/silver nanoparticle embedded poly(vinyl alcohol) hybrid nanofibre mats as active wound dressings via dual-spinneret electrospinning

AP loaded PCL/AgNP embedded PVA hybrid nanofibre mats were prepared through dual-spinneret electrospinning, which altogether contributed to wound healing.

A novel preparation of anti-layered poly(vinylalcohol)–polyacrylonitrile (PVA/PAN) membrane for air filtration by electrospinning

Schematic for the preparation of PAN/PVA membrane deposited on the stainless steel mesh modified by dilute PVA solution.